Multi-phase DC-DC converter with shared control

ABSTRACT

An increasing number of phases in multiphase converters causes an increase in requirements with respect to the control IC. According to the present invention, instead of deriving a new PWM signal for every single phase of the DC-DC converter, the single phases are clustered into groups ( 22, 24, 26 ). Within each group, the converters are operated on the basis of one PWM signal (PW M 1 , PW M 2  . . . PW MN). Advantageously, this may allow to reduce the requirements with respect to the control IC and thus may allow the application of cheaper and smaller control ICs.

The present invention is generally related to the field of powerconversion and control and, more particularly, is related to amultiphase DC-DC converter device and method.

Various DC-DC converters, such as switch mode power converter circuits,are known in the art, including, amongst others, buck and boostconverters. Buck converters operate to step down a direct current (DC)voltage from one level to another lower level, while boost convertersoperate to step up a DC voltage from one level to a higher level. Theseconverter circuits are well known and are relatively simple and operateat high efficiency, but they are limited in power handling capacity, dueto the ratings of the solid state switching devices used, such as fieldeffect transistors (FETs) and insulated bipolar gate transistors(IBGTs). For this reason, operation at high power levels may requirethat multiple switching devices are operated in parallel. Similarly, theinductors required are easy to produce and more economical in smallersizes, so that it is common practice to use both paralleled switchingdevices and parallel inductors in converter circuits, designed tooperate at relatively high power levels. While this parallel operationof components allows operation at the desired high power levels, it doesnothing to reduce the high level of ripple current in voltage producedat the input and output terminals of these converters.

EP 1 248 354 A1 discloses a multiphase converter with balanced currentsincluding a plurality of converter channels. Each converter channelcomprises one converter. Each converter is provided with its ownrespective PWM signal, generated by a control circuit. The controlcircuit includes a plurality of control circuit channels, each of whichcorresponds to a converter channel.

Such known multiphase converters may allow to reduce the output voltageripple under steady state conditions. Thus, the number of outputcapacitors necessary to filter the output signals of such convertersmight be reduced. The phase shift between the different phases, i.e. thedifferent channels of such DC-DC converters may also lead to smallerripples at the inputs of the converter, and thus smaller and cheaperfilters may be provided at the inputs.

Due to increasing load requirements for the DC-DC converters, forexample, a load current of high speed digital ICs, such as highperformance Pentium processors for PCs, may increase up to almost 100 Aat 1,0 to 1,5 Volts, there is a trend to share the currents between anincreasing number of phases. Assuming a current level of 10 to 15 A perphase, DC-DC converters need eight to ten phases to satisfy such powerdemands.

However, with the increase of the number of phases of the DC-DCconverter, the requirements with respect to the control IC becomegreater and greater, due to the fact that more and more PWM signals andsense signals are needed for the increasing number of phases.

It is an object of the present invention to provide for a simple andefficient DC-DC conversion.

According to an exemplary embodiment of the present invention, thisobject may be solved by a multiphase DC-DC converter device, as setforth in claim 1, comprising a control circuit generating a firstcontrol signal and a second control signal. Furthermore, there isprovided a first group of converters, comprising a plurality of firstconverters and a second group of converters, comprising a plurality ofsecond converters. The first group of converters is provided with thefirst control signal, such that the plurality of first converters isoperated on the basis of the first control signal and the second groupof converters is provided with the second control signal, such that theplurality of second converters is operated on the basis of the secondcontrol signal.

In other words, according to this exemplary embodiment of the presentinvention, instead of deriving a new control signal, such as a PWMsignal, for every single phase of the DC-DC converter, the phases areclustered into groups. According to an aspect of this exemplaryembodiment of the present invention, each group uses one control signal,i.e. in case the control signal is a PWM signal, only one PWM signal.Advantageously, this allows to simplify the requirements for the controlcircuit, which may allow for the provision of smaller and cheapercontrol circuits. Furthermore, the multiphase DC-DC converter deviceaccording to this exemplary embodiment of the present invention,advantageously allows for a sharing of load currents across severalphases, i.e. several converters of the DC-DC converter device and allowsfor an introduction of phase differences between the groups ofconverters to minimize input ripples. This may allow to use smaller andcheaper filters. These advantages, according to an aspect of thisexemplary embodiment of the present invention, may be obtained by usingonly a simple control IC, for example, by using a three phase controllerIC for a nine phase system, wherein the nine phases are clustered intothree groups.

According to another exemplary embodiment of the present invention asset forth in claim 2, at least one of the first converters of the firstgroup is provided with a delay circuit for time delaying the firstcontrol signal and at least one of the second converters is providedwith a second delay circuit for time delaying the second control signal.Thus, according to this exemplary embodiment of the present invention,converters of the first and second group may be provided withrespectively delayed control signals, whereas other converters of thefirst and second converters are provided with the undelayed controlsignals. In other words, in each group there is a converter, which isprovided with a direct control signal without time delay. This is adirectly controlled phase of the respective group. For the non-directlycontrolled phases or converters of the respective group, i.e. thoseconverters provided with a time delayed control signal, a phase shiftmay be introduced by controlling or setting the respective delay time.

According to another exemplary embodiment of the present invention asset forth in claim 3, each of the non-directly controlled phases orconverters of a group is provided with a delay circuit, such that adifferent time delay is introduced into the control signal for each ofthese non-directly controlled converters. Advantageously, this may allowfor a greater number of phases, while keeping the requirements for thecontrol IC low.

According to another exemplary embodiment of the present invention asset forth in claim 4, a duty cycle of a PWM signal of the first controlsignal is adapted on the basis of a first sense signal of a directlycontrolled converter of the first group. Advantageously, due to the factthat according to this exemplary embodiment of the present invention,only a reduced number of sense signals is used to adjust a duty cycle ofa PWM signal of a first control signal for a plurality of converters ofthe same group, the requirements for the control IC or for the controlcircuit may be kept low, while allowing for a controlled currentsharing.

According to another exemplary embodiment of the present invention, thefirst and second converters are boost converters, buck converters orbuck-boost or forward converters or flyback converters.

According to another exemplary embodiment of the present invention asset forth in claim 6, a method is provided for performing a DC-DCconversion. According to this exemplary embodiment of the presentinvention, a first group of converters, including a plurality ofconverters and a second group of converters comprising a plurality ofconverters are respectively provided with a first control signal and asecond control signal. According to an aspect of this exemplaryembodiment of the present invention, all the converters in each groupare controlled on the basis of the same control signal.

Advantageously, this may allow for a very simple and efficient DC-DCconversion, requiring only a minimal number of control signals, such as,for example, PWM signals.

Claims 7 to 9 provide for further exemplary embodiments of the exemplaryembodiment of the method according to the present invention as set forthin claim 6.

It may be seen as the gist of an exemplary embodiment of the presentinvention that, instead of deriving a new control signal, such as a PWMsignal, for every single phase of a DC-DC converter, the single phasesof the DC-DC converter are clustered into groups. All phases within agroup are controlled on the basis of the same control signal. Accordingto an aspect of the present invention, the non-directly controlledphases may be controlled by using a time delayed version of the controlsignal of the respective group. Furthermore, for a better currentsharing, sense signals from the directly controlled phases, i.e. thephases receiving the control signal without time delay, may be used torespectively adapt, for example, a duty cycle of the non-directlycontrolled phases.

These and other aspects of the present invention will become apparentfrom and elucidated with reference to the embodiments describedhereinafter.

Exemplary embodiments of the present invention will be described in thefollowing, with reference to the following drawing:

FIG. 1 shows a simplified schematic representation of an exemplaryembodiment of a multiphase DC-DC conversion device according to thepresent invention.

FIG. 1 shows a simplified schematic representation of an exemplaryembodiment of a DC-DC converter 2 according to the present invention. Inspite of the fact that the converters of this exemplary embodiment arebuck converters, the present invention may also be practiced with othersuitable converters such as boost converters or buck-boost or forwardconverters or flyback converters. Reference numeral 4 in FIG. 1designates an input terminal of the multiphase DC-DC converter 2according to an exemplary embodiment of the present invention, whichreceives the input signal, i.e. the input voltage from an input filter,which is not shown in FIG. 1. Reference numeral 6 designates the outputof the multiphase DC-DC converter 2. Reference numerals 8, 10, 12, 14,16 and 18 designate single phase DC-DC converter devices, such as buckconverters. The input of each of the converters 8, 10, 12, 14, 16 and 18is connected to the input terminal 4. The output of each of theconverters 8, 10, 12, 14, 16 and 18 is connected to an output terminalto form the output 6. The converters 8, 12 and 16 are directlycontrolled converters representing directly controlled phases of theDC-DC converter 2. Each of the directly controlled converters 8, 12 and16 is provided with an individual PWM signal, PWM 1, PWM 2 and PWM N.Each of the directly controlled converters 8, 12 and 16 is adapted tocontrol its output voltage and/or current on the basis of the respectivePWM signal, PWM 1, PWM 2, PWM N. Buck converters are sufficiently knownin the art, such that a detailed description of the operation ofconverters may be omitted here.

Furthermore, as may be taken from FIG. 1, a sense signal Sense 1, Sense2 and Sense N is taken from each of the directly controlled converters8, 12 and 16 and fed into a control IC 20. These sense signals, Sense 1,Sense 2 and Sense N are used to adjust the respective control signals,PWM 1, PWM 2 and PWM N in order to achieve an equal current sharingamong the individual converters 8, 12, and 16.

The voltage at the output 6 is controlled or regulated by the control IC20 by controlling the duty-cycles of the PWM . . . PWM N signals.

In FIG. 1, the directly controlled converter 8 and a non-directlycontrolled converter 10 form a first group 22. A non-directly controlledconverter represents a non-directly controlled phase of the DC-DCconverter 2.

The non-directly controlled converter 10 receives the same controlsignal PWM 1 as the directly controlled converter 8. However, incontrast to the directly controlled converter 8, the non-directlycontrolled converter 10 receives the PWM 1 signal with a time delayintroduced by a delay circuit 28. In other words, in the non-directlycontrolled phase, a corresponding time delay is introduced in thecontrol signal PWM 1 to obtain a phase shift between the directlycontrolled converter 8 and the non-directly controlled converter 10.Furthermore, as may be taken from FIG. 1, there is no sense signal takenfrom the non-directly controlled converter 10 and fed into the controlIC 20. Instead, the sense signal Sense 1 from the directly controlledconverter 8 may be used for controlling the duty cycle of the timedelayed control signal PWM 1, supplied 20, to the non-directlycontrolled converter 10 in order to control the current sharing betweenthe phases within this group.

Furthermore, there is provided another group 24, comprising the directlycontrolled converter 12 and the non-directly controlled converter 14,receiving the control signal PWM 2 with a time delay introduced by delaycircuit 30. As in group 22, the sense signal Sense 2 of the directlycontrolled converter 12, which is fed into the control IC 20, may beused to control a duty cycle of the time delayed control signal PWM 2supplied to the non-directly controlled converter 14. In the case ofgroup 22, the time delay introduced by delay circuit 30 allows to obtaina phase shift between the converters.

Furthermore, there is provided a group 26, comprising the directlycontrolled converter 16, of which the sense signal Sense N is input tothe control IC 20. Sense N may also be used to control a duty cycle ofthe PWM N signal provided to the non-directly controlled converter 18.For this, the control IC 20 may be adapted to adjust the duty cycle ofthe respective PWM signal PWM 1, PWM 2, PWM N on the basis of therespective sense signal Sense 1, Sense 2, Sense N. Also, there isprovided a delay circuit 32 for time delaying the control signal PWM N.

As indicated by the dots between groups 24 and 26, the present inventionis not limited to a certain number of groups of converters. Instead, thepresent invention may be applied to DC-DC converter devices comprisingtwo or more converter groups. Furthermore, according to an aspect of thepresent invention, not only one non-directly controlled converter may beprovided for each directly controlled converter, but a plurality ofnon-directly controlled converters may be provided for each directlycontrolled converter. For example, three, four, five or morenon-directly controlled converters may be provided for each directlycontrolled converter. Thus, for example, in case there are three groups,each group comprising one directly controlled converter and twonon-directly controlled converters, a nine phase system can be built byusing a three phase controller IC.

As may be taken from FIG. 1, according to an aspect of the presentinvention, a plurality of converters of the multiphase DC-DC converter 2are combined to a group, which is operated on the basis of the samecontrol signals PWM 1 . . . N. One converter, referred to as directlycontrolled converter of each group, is operated on the basis of thenon-time delayed control signals PWM 1 . . . N. The remaining convertersof each group are also operated on the basis of this control signal PWM1 . . . N, however, in contrast to the directly controlled converter,the control signal PWM 1 . . . N is provided to these non-directlycontrolled converters with a time delay introduced by delay circuits 28,30, 32. By controlling these time delays introduced by the delaycircuits 28, 30, 31, phase shifts with respect to the respectivelycontrolled converter of each group, may be controlled. Thus, bycontrolling the phase shifts between the control signals PWM 1 . . . .N, i.e. by controlling the respectively introduced time delays, thephases of the converters 8, 10, 12, 14, 16 and 18 may be controlled suchthat they each operate at a difference phase. Preferably, the phases ofthe respective converters are controlled such that the phase differencebetween all the converters is equal. Accordingly, due to the fact thatonly a reduced number of control signals PWM 1 . . . N is needed. Thus,the requirements for the control IC 20 are significantly reduced, andsmaller and cheaper control ICs 20 may be used. Furthermore, accordingto the present invention, a load current sharing across several phasesmay be achieved. Furthermore, phase differences may be introduced intothe control signals PWM 1 . . . N or by the delay circuits 28, 30 and 32to minimize input and output ripples. This may allow for cheaper inputand output filter arrangements. Due to this, the DC-DC converter device2, as set forth according to this exemplary embodiment of the presentinvention, may in particular be suitable for high load currents of highspeed digital ICs, such as high performance Pentium processors for PCs,where the load current may reach up to 100 A.

1. Multiphase DC-DC converter device, comprising:—a control circuit generating a first control signal and a second control signal;—a first group of DC-DC converters comprising a plurality of first DC-DC converters and a second group of DC-DC converters comprising a plurality of second DC-DC converters;—wherein the first group of DC-DC converters is provided with the first control signal such that the plurality of first DC-DC converters is operated on the basis of the first control signal and the second group of DC-DC converters is provided with the second control signal such that the plurality of second DC-DC converters is operated on the basis of the second control signal.
 2. The multiphase DC-DC converter device of claim 1,—wherein at least one third converter of the plurality of first DC-DC converters is provided with a first delay circuit for time-delaying the first control signal; and—wherein at least one fourth converter of the plurality of second DC-DC converters is provided with a second delay circuit for time-delaying the second control signal.
 3. The multiphase DC-DC converter device of claim 2,—wherein a plurality of the third DC-DC converters is respectively provided with first delay circuits, wherein the time-delays introduced by the first delay circuits with respect to the first control signal are different for each of the first delay circuits;—wherein the time-delays introduced by the first delay circuits correspond to desired phase shifts of the first control signal such that the plurality of first DC-DC converters are respectively operated at different phases of the first control signal;—wherein a plurality of the fourth DC-DC converters is respectively provided with second delay circuits, wherein the time-delays introduced by the second delay circuits with respect to the second control signal are different for each of the second delay circuits; and—wherein the time-delays introduced by the second delay circuits correspond to desired phase shifts of the second control signal such that the plurality of second DC-DC converters are respectively operated at different phases of the second control signal.
 4. The multiphase DC-DC converter device of claim 2,—wherein a duty cycle of a PWM signal of the first control signal is adapted by the control circuit on the basis of a first sense signal of a fifth converter of the first group of DC-DC converters; and wherein the fifth converter is provided with the undelayed first control signal.
 5. The multiphase DC-DC converter device of claim 1,—wherein the plurality of first and second DC-DC converters are selected from the group consisting of boost DC-DC converters, buck DC-DC converters, buck-boost DC-DC converters, forward DC-DC converters and flyback DC-DC converters.
 6. A method of performing a DC-DC conversion, the method comprising the steps of:—generating a first control signal and a second control signal in a control circuit;—providing a first group of DC-DC converters with the first control signal such that a plurality of first DC-DC converters of the first group of DC-DC converters is operated on the basis of the first control signal; and—providing a second group of DC-DC converters with the second control signal such that a plurality of second DC-DC converters of the second group of DC-DC converters is operated on the basis of the second control signal.
 7. The method of performing a DC-DC conversion of claim 6,—wherein at least one third converter of the plurality of first DC-DC converters is provided with a time-delayed first control signal; and—wherein at least one fourth converter of the plurality of second DC-DC converters is provided with a time-delayed second control signal.
 8. The method of performing a DC-DC conversion of claim 7, further comprising the steps of:—introducing time delays into the first control signal of a plurality of the third DC-DC converters, wherein the time-delays introduced in the first control signal are different for each of the plurality of third DC-DC converters;—wherein the time-delays introduced in the first control signal correspond to desired phase shifts of the first control signal such that the first DC-DC converters are respectively operated at different phases of the first control signal; and—introducing time delays into the second control signal of a plurality of the fourth DC-DC converters, wherein the time-delays introduced in the second control signal are different for each of the plurality of fourth DC-DC converters;—wherein the time-delays introduced in the second control signal correspond to desired phase shifts of the second control signal such that the second DC-DC converters are respectively operated at different phases of the second control signal.
 9. The method of performing a DC-DC conversion of claim 6,—wherein a duty cycle of a PWM signal of the first control signal is adapted on the basis of a first sense signal of a fifth converter of the plurality of first DC-DC converters; and—wherein the fifth converter is provided with the undelayed first control signal. 